1. Field of the Invention
This invention relates to a TV broadcast system, which using multiplexed and duplex, communication and verification methods, directs and controls from a central continuity studio, one or more remote stand alone TV transmitters to change and/or modify the content of their local broadcast material.
Thus it is possible to direct the local broadcast to switch between the general broadcast program or a previously stored (at the remote site) live video. Moreover it is possible to superimpose on the video being broadcast, alphanumeric character and/or image data, which are also previously stored at the remote site.
The control signals for one or more local TV broadcasts are transmitted simultaneously to remote (TV) stations either as a control signal mutual to all remote sites or separate control signals to selected remote sites by superimposing these signals on the blank horizontal lines occurring during vertical retrace period of each TV picture frame, using Teletext facilities.
The alphanumeric character and/or image data to be broadcast locally by superimposition on live video, are produced at the central studio and are down loaded to the storage facilities at the remote site over modem links.
The storage medium is usually a hard disk if only alphanumeric/image data is to be stored locally or an optical disk if live video is also to be stored locally with or without the alphanumeric/image data superimposed over it at the production site.
2. Related Art
In current practice, remote stand alone TV transmitters rebroadcast over an VHF or an UHF (or a cable) channel, the general TV broadcast of a particular TV network.
However by this method it is not possible to change the local broadcast content at desired times, to change and/or add to, the video broadcast to satisfy local requirements.
In order to accomplish this objective at remote TV transmitters, A TV network has to use local, manned studios, employing manual equipment.
For the large TV network establishments, it usually, is not economical to establish manned local studios at each remote broadcast area.
In practice there can of course be independent local TV broadcasters where economically feasable, but they are usually independent of a large TV network establishment and thus cannot use their program material.
It is also possible to achieve a degree of automation by switching the video program transmission to prerecorded material on videotape by controlling VCR(s) through a computer which is constantly monitoring the duration of a particular program and the real time clock. This method is often used for late night broadcast of programs
The TV transmission systems in use, include blank horizontal scan lines during vertical retrace period. these blank lines may be used depending on the choice of the broadcaster for, either Teletext, Data Broadcast or VPS.